sewage sludge management in egypt - ghazy 2009

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AbstractThe present disposal routes of sewage sludge representa critical environmental issue in Egypt. Recently, there has been anincreasing concern about sewage sludge management due to theenvironmental risks, which resulted from the fast expansion of

wastewater treatment plants without equal attention in dealing withthe produced sludge. This paper discusses the current situation ofsewage sludge management in Egypt presenting a brief overview ofthe existing wastewater treatment plants, sludge production andcharacteristics as well as options of beneficial use and potentialdemand of sewage sludge under Egyptian conditions. Thecharacteristics of sewage sludge are discussed considering the resultsof own sampling and analysis as well as previous studies.Furthermore, alternative treatment scenarios for sewage sludge,which have been recently developed in Egypt, are discussed andperspectives for a sustainable agricultural use are outlined.

KeywordsBeneficial use, Egypt, Monetary value, Stabilizationprocesses, Sewage sludge, Sludge management.

I. INTRODUCTIONEWAGE sludge is composed of constituents collected or

produced at different stages of the wastewater treatment

process. It contains compounds of agricultural value

(including organic matter, nitrogen, phosphorus and

potassium) and a lesser amount of calcium, sulphur and

magnesium. Moreover, it may also contain pollutants such as

heavy metals, organic pollutants and pathogens. The handling

of sewage sludge is one of the most significant challenges in

wastewater management. In many countries, sewage sludge is

a serious problem due to its high treatment costs and the risks

to environment and human health. Although, the volume of the

produced sewage sludge represents only 1 % to 2% of the

treated wastewater volume, its management costs are usually

ranging from 20% to 60% of the total operating costs of the

wastewater treatment plant [1].

Due to the currently low capacities of wastewater treatment

prevailing in many developing countries, a future increase in

Authors are with Institute of Sanitary and Environmental Engineering,Technische Universitt Braunschweig, Pockelsstr. 2a, 38106 Braunschweig,

Germany (phone: +49(0)531-391-7936; fax. +49(0)531-391-7947, web:

http://www.tu-braunschweig.de/isww, e-mail: [email protected],[email protected], [email protected]).

the number and capacities of wastewater treatment plants can

be expected. As a consequence, the amount of produced

sewage sludge is also expected to increase. The produced

sludge from developing countries usually differs from which

generated in developed ones due to divergent industrialization

and public health levels. In developing countries, the metaland toxic content is usually much lower, while pathogens

content is much higher [2]. These aspects show that, sewage

sludge management is an increasing matter of concern in many

countries due to the fast increases in sludge production, which

increases the resulting environmental threats accordingly.

Sewage sludge is produced under different technical,

economical and social contexts. Thus requiring different

treatment approaches, which should be flexible enough to be

applied under different circumstances, taking the different

regulations as well as geographical, economical, social and

cultural constrains into account [3]. It clearly appears, the

development of optimal sludge management proceduresrequires adapted management routes capable of maximizing

the recovery benefits. It also requires developing operational

systems appropriate to local conditions. Moreover, it needs to

develop realistic and enforceable regulations adapted to local

situations and assuring long-term services and sustainable

treatment processes [4].

Since a long period, Egypt has been concentrating its efforts

on sanitation services mainly on wastewater treatment, while

little priority has been given to sludge management in practice.

The primary focus of investment has been addressed to water

supply, sewerage networks and wastewater treatment. Until

2004, the percentage of population served by wastewater

facilities was very low. More than 80 % of the rural areas and

about 40 % of the urban areas are showing deficits in adequate

sanitation facilities [5]. Currently, a quite small attention is

given to sludge management, which is reflected in the local

legislations that often simply depend on regulations of

industrialized or more advanced countries without any attempt

to adapt it to local situations.

II. BRIEF OVERVIEW OF WASTEWATER TREATMENT PLANTS INEGYPT

The Egyptian population has tripled during the last 50 years

and still grows each year by approximately 1.5 million people.

The total population increased from 22 millions in 1950 to 80

Sewage Sludge Management in Egypt: Current

Status and Perspectives towards a SustainableAgricultural Use

M. Ghazy, T. Dockhorn, and N. Dichtl

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World Academy of Science, Engineering and Technology 33 2009

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millions in 2008, and is likely to increase to above 96 millions

by 2026 [6]. With the rapidly growing population and

industrial development, wastewater generation has been

increased and is also expected to increase significantly in the

future. The Egyptian sanitation sector is facing many

difficulties to manage this wastewater mainly due to financialproblems, which require huge investments far above the

presently available national resources. The Government of

Egypt has invested more than 24 billion US$ in development

of water and wastewater services over the last 20 years and

plans to invest about 20 billion US$ in the next 10 years [7].

More than 56 % of Egypts population (45 million in 2007)

live in rural areas, in 4600 villages, mainly concentrated in the

Nile Valley and Delta [8]. Only less than 10 % of them have

access to wastewater collection and treatment facilities, the

wastewater from households in these rural areas are mainly

primary treated in septic tanks [9]. On the other hand, 44 % of

Egypts population (35 million in 2007) live in urban areas, in217 cities. Until 2004, only 57% of them had access to

wastewater collection and treatment facilities.

During a site visit and field study of Egypts wastewater

treatment plants (WWTPs) in 2008, a data survey from many

sources such as the Holding Company for Water and

Wastewater (HCWW), the National Organization for Potable

Water & Sanitary Drainage (NOPWSD) and the WWTPs in

Cairo and Alexandria was conducted. The total number of

WWTPs in Egypt is 303 treating 11.85x106 m3/day of

wastewater. Table I shows the number and capacities of

WWTPs in Egypt and the estimated amount of sewage sludge

generated in 2008.

TABLEI

SCALES OF WWTPS AND AMOUNT OF SLUDGE GENERATION IN EGYPT(YEAR 2008)

Range of WWTPcapacities

(103 m3/day)

Numberof

WWTPs

Total treatedwastewater

capacity(103 m3/day)

Amount ofsewage sludge

generation(ton DS /day)

>8 79 198 64

8 - 15 90 917 453

15 - 30 70 1425 683

30 - 100 44 2121 1010

100 - 500 15 2895 1445

500 - 1000 4 2600 1300


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1. Stabilization Process by Using Anaerobic Digestion

This scenario has been applied in Al Gabel Asfer WWTP,

which is the biggest wastewater treatment plant in Egypt. The

current sewage treatment capacity is 1800x103 m3/day and will

be increased to 3000x103 m3/day in 2020. The application of

the anaerobic digestion technology for sludge stabilization and

power generation in Al Gabel Asfer WWTP has achieved

good results and many experiences in operation and

maintenance have been gained. Thus, there is an interest in

using such technology on large scale in Egypt, especially in

big wastewater treatment plants in major cities. Fig. 2 shows

the flow diagram of sewage sludge treatment and disposal

scenario using the anaerobic digestion processes in Al Gabel

Asfer WWTP.

In this scenario, the mixed sewage sludge (primary and

secondary sludge) is pumped to thickening facilities (16

gravity thickeners with a volume of 3,200 m3 and 3 thickeners

with a volume of 2,500 m3

each). After the gravity thickening,the thickened sludge (12500 m3/day, conc. 4 % DS) is pumped

to primary digesters (20 anaerobic digesters with a volume of

11,000 m3 and 8 digesters with a volume of 9,750 m3 each) for

a retention time of 20 days. Then, the sludge is transferred to

secondary digesters (10 digesters with a volume of 7,550 m3

and 2 digesters with a volume of 8,752 m3 each) with a

retention time of 7 days, where the decanting of liquors can be

accomplished. After that, the digested sludge is pumped to

mechanical dewatering facilities (30 belt filter press units with

a capacity of 23 m3/hr and 12 units with a capacity of 21 m3/hr

each) for dewatering. The total solids concentration in the

dewatered sludge cake ranges between 23-30 %. Trucks

transfer this cake (450 tons/day) for drying in a stacking area

to a concentration of 40-60 % DS before its use in agriculture.

The large portion of the produced biogas is currently used for

the operation of hot water boilers, which are operated to heat

the raw sewage sludge in the primary digesters. Dual fuel

generators use the excess digested gas to generate electricity

representing about (37-68%) of the power consumed by the

WWTP.

2. Stabilization Process by Using Windrow Composting

The windrow composting of dried sewage sludge is another

recently applied scenario for sludge treatment in Egypt, as

already applied in the Al Berka WWTP in Cairo and the (9N)

site in Alexandria. Fig. 3 shows the general flow diagram of

the sludge treatment and disposal scenario using windrow

composting in Al Berka WWTP and (9N) site.

The composting begins with collection of suitable organic

materials that are mixed to achieve the desired C:N ratio,

moisture content and pore space. Usually, sewage sludge is the

primary material and one or more amendments are added to itsuch as rice straw as applied in Al Berka WWTP or old

compost as applied in (9N) site. According to the Egyptian

conditions (dry and warm weather mostly of the year) good

bacteriological results were achieved in the produced compost

as evaluated by several laboratory analyses [10].

Fig. 3 Flow diagrams of the sludge treatment scenario by using

windrow composting

a. AL Berka WWTP Compost Pilot Project

The pilot project in Al Berka WWTP is an experimental

compost project that was initiated in 2007 to treat 140 m3/day

of dry sewage sludge produced from the drying beds in Al

Berka WWTP using the windrow composting processes.

In this pilot project, a mixture of dried sludge produced atAl Berka WWTP drying beds and rice straw are composted in

long parallel rows (stacking) or windrows. A total of 12 tested

windrows have been formed. The ratio of dry sludge, old

compost and rice straw are varied widely to select the best

combination ofingredients (feed stocks). The composting time

was about 3 months. The laboratory analyses of the tested

windrows are attached. Some pathogens remained in certain

windrows, while most of the pathogens could be removed. For

the full-scale project, it is planed to construct larger windrows

and the residence time will shorten to be 4-8 weeks followed

by 30-60 days curing period. The most probable compost ratio

by using a volumetric ratio was 4 parts sludge (25% DS): 1

part finished old compost (60% DS): 1 part shredded rice

Biogas

(37-68 % ) of WWTP Electricity

Electricity from

main Grid network

Gravity Thickener

Anaerobic digestionMechanical Dewatering

Agricultural Reuse

Activated sludge WWTP

Sludge stacking area

Engine Generators &Switch gear((Energy recovery))

Heat Exchange

Blending chamber

Fig. 2 Flow diagram of the sludge treatment scenario by using anaerobic digestion technology


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straw (85% DS). This ratio has given good results in the tested

windrows.

The experimental composting project in Al Berka WWTP

(2600 m2) is now fully adequate to serve as a commercial

project. The equipments and staff are adequate to sustain the

production of about 70 tons of compost per day, whichrepresents about 66% of the produced sludge from the drying

beds in Al Berka WWTP.

According to the Egyptian Government future plan, after

the evaluation of the final results of each experimental and

commercial pilot project, Al Berka composting pilot project

may be expanded to a full-scale project to produce a compost

of 720 tons per day from the dried sewage sludge accumulated

from Al Berka, Shobera and Al Gabel Asfer WWTPs [10].

b. (9N) Site Sludge Treatment Scenario

The main WWTPs in Alexandria governorate are the East

WWTP with a present sewage capacity of 490x103 m3/day and

the West WWTP with a capacity of 360x103 m3/day. Both of

them are still using only primary sewage treatment processes.

The primary sludge produced at the Alexandria East and West

WWTPs (3000 m3/day, conc. of 3.8-5.25% DS) are

mechanically dewatered by belt filter presses as applied in Al

Gabel Asfer WWTP. Polymers (2-4 kg/ton DS) are used to

produce a dry sludge cake of 580 tons/day with a solid

concentration of 25-30 %. Trucks transfer this cake over a

distance of 45 km to the central site for sludge treatment at

(9N) site to complete the sludge treatment processes by using

windrow composting facilities.

The (9N) site is a central sludge treatment place for all

sludge produced from Alexandrias WWTPs. The site hasbeen operating since 1997 with composting windrow

processes. The site area is 1.51 km2 and is located in the

southwest of Alexandria city. The windrows are formed in two

composting areas (each of 0.29 km2), where the dry sludge is

mixed with a bulking agent (old compost) with a ratio of 1.5:1

in long parallel rows (250 m length each). The width of a

typical windrow is 2 to 4.5 m at the base and the height is 1 to

2 m. The composting period is about 1-2 months and the

windrows are turned every 7 days by a special mechanical

turning machine. The temperature in the central portion of the

windrow reaches 55 to 70C. Currently 112x103 tons of

compost are produced each year [11].3. Stabilization Process by Using Sludge Storage Lagoon

The third developed scenario for sewage sludge treatment in

Egypt was applied in Abu Rawash area for treating the sewage

sludge generated from Zenin and Abu Rawash WWTPs. Fig.

4 shows the flow diagram of sludge treatment and disposal

scenario using a sludge storage lagoon. The storage lagoons

hold the sewage sludge under anaerobic or aerobic conditions

over a long period, typically 1 to 4 years. During storage, the

sewage sludge is pretty decomposed and pathogens are

destroyed [12].

Fig. 4 Flow diagram for sludge treatment scenario using storage

lagoons

In this scenario, the mixed sludge produced from the

conventional activated sludge system in Zenin WWTP (20x103

m3/day, conc. 0.5% DS) is pumped into a main sludge pump

station in Abu Rawash WWTP. Then it is mixed with the

primary sludge produced from the primary treatment facilities

in Abu Rawash WWTP (1560 m3/day, conc. 4.7 % DS). After

that, the mixed sewage sludge is pumped through a force main

pipe of 800 mm diameter over a distance of 33.3 km to the

natural sludge storage lagoons (20 lagoons), which are situated

at a desert area of 2.32 km2 in Abu Rawash area.

IV. SLUDGE PRODUCTION AND CHARACTERISTICSCurrently, except Cairos WWTPs, there is very limited

information about the actual sewage sludge production and

characteristics for all Egypts WWTPs.

A. Sludge Production and Quantities

TABLEIIESTIMATED DRY SLUDGE PRODUCED FROM ALL WWTPS IN EGYPT,2008

Estimated drysewage sludge

(50 % DS)

Amount Volume

Type of WWTPsNo of

WWTPs

Sludgeproduction

rate(kg/m3)

Capacity oftreatedwastewater103 m3/day

tons/day m3/day

Activated Sludge 97 0.225 6,703 1,508 2,793

Oxidation Ditch 47 0.225 833 187 347

Trickling Filter 9 0.22 291 64 119

Extended Aeration 17 0.1 170 17 31

Oxidation Ponds 35 0.05 266 13 25

Aerated Lagoon 4 0.1 197 20 36

Primary Treatment 22 0.15 2,021 303 561

Others* 72 0.2 1,372 274 508Total 303 11,853 2,387 4,421

Assume: the dry solid content is 50 % and the average density of dry sludge1.08 ton/ m3.

Others*: types of WWTPs where the data about their system of treatment ismissing.

Currently, Egypt has 303 wastewater treatment plants thathandle 11.85x106 m3/day of sewage. The corresponding drysewage sludge production was estimated to 5.8x103 tons/day(according to the NOPWSD and HCWW data) with a sludgeproduction rate of 0.48 kg/m3 of treated wastewater. Whichseems relatively high compared to other typical valuesreported in some references [13]-[15]. In the current study, the

results of some previous studies for sludge management in


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Cairo are analyzed to evaluate and estimate a reliable amountof the produced sewage sludge from all Egypts WWTPs [10],[11], [20]. Furthermore, the sewage sludge production rate hasbeen also theoretical calculated according to the Germanstandard and Metcalf & Eddy (2003) based on BOD and TSS

concentrations [16]-[18]. Based on the results of previouscalculations, the dry sludge production rate of the activatedsludge treatment plant systems in Egypt is considered at 0.225kg/m3 of treated wastewater and the production rates of theothers WWTP types are assumed at 0.05-0.22 kg/m3 accordingto the literatures [18]. Table II Indicates the estimated amountof dry sewage sludge produced at all Egyptian WWTPs in2008.

B. Sludge Quality and Characteristics

Currently, there are only a few wastewater treatment plants

in Egypt that have information about their sludge

characteristics. During the field study, dry sewage sludge

samples were collected from the WWTPs in Cairo andAlexandria and were analyzed according to standard methods.

The characterization of sewage sludge was focused on the

following parameters:

1. Heavy Metals

TABLEIII

CONCENTRATION OF HEAVY METALS (MG/KG) IN DRIED SEWAGE SLUDGE INEGYPT

WWTP Ref. Zn Cu Pb Cd Cr As Hg Ni

Abu RawashFieldstudy

1,810 321 218

Others*113-4,639

83-515 38-5094,6-50

779 4-250,5-15

25-212

Fieldstudy

1370 497 15,800Al Berka

Others112-6,298

257-2,640

26-1,119

2,5-40

3330,4-30

3,7 5-645

Field

study1640 639 1,320

Al GabelAsfer

Others132-1,176

339-74751-

1,7240,9-6,21

312-993

0,2-28

0,1-10

43-215

Fieldstudy

804 220 384(9 N) Site

Alex.Others 540-901 234-418 191-310 4-100 89 9 16

57-

100

Shobera Others 232-604 63-322195-1213

4,4 130 0,3 7,7 29

Helwan Others155-

8,097

119-988 50-30215-

312

17223-

188Egyptian standards 2,800 1500 300 39 1,200 41 17 420

Others*: results of sampling analysis of previous studies (METAP, 1999 [20],AFESD, 2007 [10], NOPWASD and HCWW data).

The level of heavy metal contamination is the first

parameter that must be assessed to determine the overall

quality of sewage sludge and is very important in case of using

it for land application. Generally the Egyptian WWTPs dont

have high heavy metal contamination in the produced sewage

sludge. Although, high heavy metal contamination rates were

detected in few isolated cases, those metal contaminations are

related to irregular contributions from industrial areas. Table

III lists the heavy metal contents in dry sewage sludge

collected from Cairo and Alexandria WWTPs.

It is expected that the concentrations of the heavy metals in

other WWTPs in Egypt are lower than the concentrations

shown in Table III. The investigated WWTPs were in Cairo

and Alexandria governorates where industrial activities are

more concentrated. Recently, several new industrial zones arecreated in other cities, so that the concentration of industrial

activities in Cairo and Alexandria governorates might be

reduced in the future.

2. Nutrients Content

The sewage sludge contains nutrients including organic

matter, nitrogen, phosphorus and potassium. These nutrients

favour its agricultural use. According to the results of sample

analysis and other previous studies, the nutrient contents in the

dry sewage sludge in Egypts WWTPS were as shown in

Table IV.TABLEIV

CONCENTRATION OF NUTRIENT RESOURCES IN THE DRIED SEWAGE SLUDGEIN EGYPT

Reference

Totalorganicmater

(OM) %

Totalnitrogen(TKN) %

TotalPhosphorus

(P) %

Potassium(K) %

Field study, 2008 57 3.16 1.13 0.28

AFESD, 2007 61 3.13 0.65 0.19

IIP, 2002 2.4 0.55 0.3

NOPWASD, 2000 61 4.11 1.6 0,55

METAP, 1999 45 1.7 0,8 0.3

Average 56 2.90 0.95 0.32

Sources: (IIP study, 2002[19], METAP, 1999 [20], AFESD, 2007 [10] andNOPWASD data).

3. Pathogenic Micro Organisms

TABLEV

THE PATHOGENICMICROORGANISMS PRESENCE AND LIMITS IN CAIROWWTPS

Case of sewage sludge

LiquidDry

WWTPsPathogenicmicroorgani

smsUnits

Averagevalue

UnitsAverage

value

Totalcoliform

MPNx1010/ 100mL

38.5 No data

Fecalcoliform

MPNx108

/ 100mL

23 MPN/gm 5.3x105AbuRawash

Salmonella No/ 100 mL 050 %

positive

Totalcoliform

MPNx1010/ 100mL

28.5 No data

Fecalcoliform

MPNx108/ 100mL

5 MPN/gm 1.3x106Al Berka


positive

Totalcoliform

MPNx1010/ 100mL

297.5 No dataHelwan


positive

Sources: (METAP, 1999 [20] and AFESD, 2007).


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The third parameter for determining the sewage sludge

quality is the presence or absence of pathogens. Usually, the

dried sewage sludge produced at the Egyptian WWTPs

contains a high rate of pathogenic concentrations, which

represent the most important obstacles for a safe use in

agriculture. Table V shows the pathogenic microorganismconcentrations in sludge of three WWTPs in Cairo. The

pathogenic were qualitative analysis in the dry samples.

V. BENEFICIAL USES OF SEWAGE SLUDGEHistorically, most of the sewage sludge was disposed by

land filling or applied directly to agricultural land. However

there are several factors limiting the potential of expanding the

beneficial use of treated sewage sludge. These factors include

limited public acceptance, concerns of landowners, certain

cost factors and types of crop grown. Furthermore, increasing

problems that are related to an increased input of organic

contaminants, heavy metals and pathogens into the soil andtherefore into the food chain.

A. Options for the Beneficial Use of Sewage Sludge

Alternative beneficial uses of sewage sludge are receiving

greater attention because of a decline in available landfill

space and also an interest in conserving nutrients and other

recoverable materials of sludge. Moreover, changes in public

perception and legislation worldwide are likely to make

disposal to landfill less popular. Furthermore, marine disposal

has been stopped in almost all countries [13]. The future focus

is likely to be incineration (and other forms of thermal

processing) and agricultural use in many countries.

The beneficial use of sewage sludge in most of thedeveloping countries as a soil conditioner or for land

application can be considered as a good option. Especially, the

land degradation problems and insufficient food production as

well as the financial problems are considered. The land

degradation costs between 5 to 10% of the agricultural

production and 50 to 60 thousand km2 per year of arable land

are being lost through soil degradation [21]. The sewage

sludge contains nutrients and organic matter, which are useful

for soil conditioning to improve soil properties and to promote

plant growth. Sewage sludge generally has lower nutrient

contents than commercial fertilizers. Nevertheless, the use of

sewage sludge in agriculture reduces the need for commercialfertilizers. Furthermore, it can reduce the costs of agriculture

and the negative impacts of high levels of excess nutrients

entering the environment. Moreover, the slow-release and

long-term availability of nutrients in sewage sludge can

enhance the efficiency compared to mineral fertilizers.

There is a debate on the use of sewage sludge in agriculture,

originated mainly in Northern Europe, gaining in intensity

from 1995 onwards. This is due to the fact that some concern

was expressed about the potential risks for health and the

environment when receiving sludge in agriculture.

Nevertheless, there is still an increase in agricultural use in

many other countries. The use of sewage sludge for land

application in USA has changed from 20% in 1972 to 41% in

1998 [13], [22].

Based on the importance of agriculture in Egypt, as well as

the degree of soil erosion and necessity of land reclamation,

the land application is considered as the best and predominant

method of beneficial uses of sewage sludge under the Egyptian

conditions.

B. Sewage Sludge Agronomic Value

The agronomic value of sewage sludge depends on its

nutrients, trace elements and organic matter content. The

sludge contains agronomically valuable amounts of major

plant nutrients including nitrogen, phosphorus, potassium as

well as other macronutrients such as calcium, magnesium and

iron. It is very difficult to place actual monetary values for the

trace elements or organic matter that are applied to soil. The

organic matter has an important role in maintaining and

improving a wide range of soil properties that improve the

plant root environment. Plants are better able to withstand

drought conditions, extract water and utilize nutrients.

Especially in sandy soils, the addition of organic matter

increases the water holding capacity, soil aggregation and the

cation exchange capacity, which is a very important property

for supplying plant nutrients. Moreover, it reduces surface

runoff, erosion and soil bulk density [23].

According to the results of sample analysis, which were

collected from WWTPs in Cairo and Alexandria during the

field study and other previous studies, as shown in Table IV,

the average values of nutrients and organic resources in the

dried sewage sludge in Egypt were as follows: 56 % organic

matter, 2.9 % total nitrogen, 0.9 % phosphorus and 0.32 %

potassium.Theoretically, the monetary values of the resources

contained in sewage sludge can be evaluated according to the

current price of these relevant resources in the commercial

market. To determine the economic values of the resources N,

P, and K, the market prices of these elements in the

commercial inorganic fertilizers are considered. While the

monetary values of the organic matter can be estimated

according to the market price of the generated electricity

during the anaerobic digestion stabilization [24]. The

theoretical electrical generation from 1 kg of dry sewage

sludge can be calculated by 0.78 kWh/kg of dry sludge

(assuming: the quantity of digested gas obtained during the

anaerobic digestion is 1 m3/kg of volatile solids destroyed and

the lower heating value of the digested gas is approximately

6.22 kWh/m3).

The monetary value of the dry sewage sludge can be

calculated according to the current prices of the relevant

resources at the Egyptian and international markets, as shown

in Table VI. In general, the prices of commercial fertilizers in

the Egyptian market are less than those at the international

market due to the support of the Government to the fertilizer

industry by about 32 % of the industry costs.


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TABLEVITHE MONETARY VALUES USED FOR THE RELEVANT RESOURCES IN DRY

SEWAGE SLUDGE

ResoursesEgyptian

market price(US$/kg)

USA Market price(US$/kg)

Nitrogen (N) 0.76 1.61

Phosphorus (P) 2.23 4.91

Potassium (K) 0.43 0.94

Organic matter 0.015 0.044The average retail price of electricity in USA, 2008 was 10.13 Cent/kWh and

in Egypt 3.4 Cent/kWh.The exchange rate used in 2008 was US$ = 5.76 LE (Egyptian pound).

The theoretical calculated monetary value of the dried

sewage sludge in Egypt is about 53 US$/ton (28.5 US$/m3).

This value probably indicates the maximum price of the dried

sewage sludge that can be paid by farmers, including the

transport costs in the Egyptian market.C. Potential Demand of Sewage Sludge in Agriculture in

Egypt

Egypt is an arid country, the dessert represents more than

95% of the total area and only 4% are occupied by

overpopulation in a limited strip of the Nile valley and Delta.

Due to the rapid increase in population, the cultivated land

declined per capita from about 0.23 acre (acre = 4046.9 m2) in

1960 to about 0.13 acre in 1996 and will be decreased to 0.09

acre by 2017 [25]. The sharp decline of the per capita

cultivated land will also reduce the per capita crop production,

which will directly affect food security for populations. An

important issue in the future is to redistribute the populationover a larger area. Therefore, the quest to bring new land

under cultivation has been a cornerstone of Egyptian

agricultural policy since the 1950s. Over the last 30 years, the

Government of Egypt has undertaken a large programme of

horizontal expansion of agricultural used land through the

reclamation ofdesert areas. More than 3.29 million acres have

been reclaimed and that will be increased in the future[5].

The soil in these reclaimed land are often saline, mild to

moderately alkaline (pH 7.7-8.2), contain calcium carbonate in

the range from 1-20% and appreciable concentrations of

gypsum (hydrated calcium sulphate) [20]. Micronutrient

element deficiencies are common, particularly manganese,

iron and zinc due to the high pH [21]. Such soils derived under

hot arid conditions are unlikely to cultivate and contain very

little organic matter. Furthermore, the coarse nature of these

soils, dominated by gravel and sand effects a low fertility and

a low water holding capacity. There are considerable

requirements for most plant nutrients as well as additional

organic matters to improve water holding capacity, soil

structure and aeration.

Some field pilot studies involved the establishment of a

practical system for the safe use of sewage sludge in

agriculture in Egypt had been done principally through a series

of demonstration field trials and sludge quality sampling

programmes. The results of these studies indicated that, the

nutrients, trace elements and organic matter present in the

sewage sludge have the potential to increase the yield and

quality of crop and to improve the soil conditions for crop

growth under Egyptian conditions. The crop response to

sludge was equal to and often greater than that from an

equivalent quantity of farmyard manure or inorganic fertilizers[19].

The climatic and soil conditions in Egypt strongly favour

the use of sewage sludge for land application. This may be

attributed to the following factors [20].

Calcareous and clay soils limit crop uptake of heavymetals and potential toxicity

Reclaimed land is deficient in Zn and Cu as well asother essential elements, which are required for plantgrowth and are present in sludge

The extensive sunshine exposure, high temperature,and dry conditions provide aggressive andunfavorable conditions for the survival of microbialpathogens.

However, the quality of produced sewage sludge and

conditions of sludge application in Egypt should be more

controlled to ensure that the potential hazards to health and the

environmental are avoided.

D. Sewage Sludge Market in Egypt

1. Potential Market Demand

The recommended application rate of dry sewage sludge for

arable crops in Egypt ranges from 5 - 20 m3 DS/acre/year

depending on crop and soil types and frequency of application.

For fruit crops the favour application rate is 8.7 m3

DS/acre/year [19]. These values are also matching with the

recommended application rates in Egyptian standards

(Directive 254/2003) that ranged from 8-20 m3 DS/acre/year

according to the types of soil and cultivated plants [27].

There is a controversy debate in Egypt about the suitable

land that will be target for the sewage sludge application. The

reclaimed desert land can be considered more preferably

where the demand for sewage sludge on the reclaimed farms is

likely to be high and any inputs of organic matter are valuable

for water retention and nutrient supply. Moreover, the farm

size and access to farms make the supply of sludge more

practicable. Also, farm managers are often graduates or

engineers and are able to realize the benefits of sludge and theneeds for appropriate control of sludge application. At Delta

Nile farms, sludge can be also used as an alternative to farm

yard manure. But, this is likely to be constrained by the

practicability of supplying and delivering relatively small

quantities of sludge to small farms. The majority of farms in

the Nile valley and Delta are small, less than 5 acres

accounting for 96% of farms [20]. In addition, the access is

likely to be difficult for large trucks; moreover, illiteracy is

high amongst farmers that may cause hazards associated with

the agricultural use of the sludge.

To evaluate the overall potential demand of sewage sludgeon the Egyptian market, uniform average application rateshave been assumed at 10 m3/acre/year for field and fruit crops.


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The reclaimed desert land was considered as the main targetmarket where the use of sewage sludge is easier, morepractical and fewer hazards to the human health than in theNile valley and Delta areas. Furthermore, in general theestimated equivalencies of sewage sludge were higher than for

clay soil. This may be attributed to factors such as a greaternitrogen release and mineralization from sludge in sandy soilsthan in clay because of their low organic matter status andpoor physical conditions.

The theoretical quantity of dry sewage sludge which is

required to satisfy the potential demand of the reclaimed desert

land will exceed 32 million m3/year. The current dry sludge

production is estimated to be about 0.86 million tons per year

(1.59 million m3/year). This would represent only 4.9 % of the

potential cropped land required within the reclaimed desert

land only. Furthermore, the cultivated areas in the Nile Valley

and Delta represent more than 5 million acres [13]. The

theoretical need of these land is more than 50 million m3/year

of sewage sludge. Generally the use of sewage sludge inagriculture has a big and a good market in Egypt, but it must

be environmentally and socially acceptable and cost-effective.

2. Sewage Sludge Market Price

In Egyptian market, the sewage sludge is highly valuable

and the farmers are willing to pay up to around 6.4 US$/m3

according to the result of some previous studies in 1995 [20].

The suggested sales price of converted sewage sludge is 4-10

US$/m3 according to a study in 2002 [19]. Currently, the

amount of dried sewage sludge produced at the drying beds of

Al Berka WWTP is directly sold to farmers with a gate price

of 8.20 US$/m3. The sale price of the produced compost from

the pilot compost project in Cairo ranges from 8 13 US$/m3

[10]. The Egyptian Holding Company for Water and

Wastewater (HCWW) sells the produced dry sewage sludge to

main contractors with a gate price ranging from 1.5-10.5

US$/m3, with average prices of 6.1 US$/m3. The contractors

sell it after that to the farmers with a profit margin. This price

is very suitable and a competitive price compared to other

organic fertilizer in the Egyptian market, which are sold at

about 17.76 US$/m3 [10].

From the previous survey of the existing sale prices of dry

sewage sludge in the Egyptian market and the study of the

potential demand, it is noted that, there is still a big

competition margin with other organic fertilizers on themarket. The target price of sewage sludge in the Egyptian

market can be estimated at about 20 US$/ton (10.8 US$/m3).

VI. CONCLUSIONThe sewage sludge production is continuously increasing in

Egypt. Therefore, the main currently pressing needs are to

find/develop more efficient and more sustainable technologies

to allow a safe and suitable reuse of sewage sludge in

agriculture. Furthermore, the legislations should be more

adapted to the Egyptian conditions as well as improvement of

the institutional capacity to guarantee the enforcement of their

application.

For many years, the methods and technologies for sewage

sludge treatment have been implemented in Egypt were very

limited. The main attention was devoted to processes of drying

sewage sludge, mainly through natural drying beds, without

any interest in the characteristics or quality of the produced

sludge. Recently, the application of the anaerobic digestiontechnology for sludge stabilization and power generation in Al

Gabel Asfer WWTP and the windrow composting processes in

(9N) site and Al Berka WWTP have achieved good results

regarding to the produced sludge quality and also many

experiences in operation and maintenance have been gained.

There is a growing interest in using such technologies on large

scale in the future.

The use of sewage sludge in agriculture in Egypt may offer

the most sustainable and beneficial use of sewage sludge under

Egyptian conditions. It may offer the most economical route

of sludge disposal because the Egyptian farmers are prepared

to pay for any source of organic manure. About 0.66 milliontons of the dried sewage sludge have already been sold to

farmers in 2007, which represent more than 85 % of the total

produced sewage sludge from all WWTPs in Egypt according

to HCWW data.

The treated sewage sludge has a good potential demand in

the Egyptian market. The target price of municipalities is

estimated at 20 US$/ton (10.8 US$/m3) of dry sludge. This

price has still a proper competition margin up to 5 US$/ton

less than the present price of other organic fertilizers and also

less than the estimated theoretical price (28.5 US$/m3) of the

relevant resources in the dry sewage sludge under Egyptian

conditions. It must be emphasized that the sewage sludge,

which doesnt fit the standards, must be disposed at controlled

landfills and it should be prevented to use in agriculture.

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